High frequency oscillatory ventilation (HFOV): How does it work and how to integrate it in the...

High frequency oscillatory ventilation (HFOV): How does it work and how to integrate it in the concept of lung protective ventilation and of the open lung?

1) What is HFOV?Specific characteristics of HFOV

2) Basic mechanisms of gas exchange during HFOV

3) How does HFOV fit in actual concepts of lung protection?

- Basic concepts of lung recruitment during HFO

- What are optimal settings and how to monitor

- How to set MAP when switching from CMV

HFO = HFJV = HFPPV

Patient

Humidifed Bias Flow//

“Elimination” of tidal ventilation

Slutsky AS ARRD 1988;138:175-83

Gas transport mechanisms during HFOV

Bouchut JC et al. Anesthesiology 2004; 100:1007-12

Pressure transmission CMV / HFOV :

Gerstman et al

Tracheal pressure

Endinspiration Endexpiration

CMV HFOPEEP 10, Vt 6 CDP 16

CMVHFOV

CMVHFOV

Lung volumes

The Paw is used to inflate the lung and optimize the alveolar surface area for gas exchange.

Paw = Lung Volume

Oxygenation

Oxygenation is primarily controlled by the mean airway pressure (Paw) and the FiO2 for “Diffuse Alveolar Disease”.

The Paw is used to inflate the lung and optimize the alveolar surface area for gas exchange.

Paw = Lung Volume

From the lab to the bedside: The principal concepts

Adapted from Suzuki H Acta Pediatr Japan 1992; 34:494-500

Lung Recruitment Using Oxygenation during OpenLung High-Frequency Ventilation in Preterm Infants

De Jaegere Ann et al. Am J Respir Crit Care Med 2006: 174; 639–645


Lung Recruitment Using Oxygenation during OpenLung High-Frequency Ventilation in Preterm Infants

De Jaegere Ann et al. AJRCCM 2006: 174; 639–645

before surfactant after surfactant

The Open Lung Approach with HFOV(Lung-Lavaged Rabbits) McCulloch, Forkert, Froese ARRD 137:1185-1192,1988

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HFO-Hi HFO-Lo CMV

Percentage airways with lesions

4+Epithelialinjury

HyalineMembranes

Ventilation

Ventilation is primarily determined by the stroke volume (Delta-P) or the frequency of the ventilator.

Alveolar ventilation during CMV is defined as:

F x Vt

Alveolar Ventilation during HFV is defined as:

F x Vt 2

Therefore, changes in volume delivery (as a function of pressure-amplitude, frequency, or % inspiratory time) have the most significant affect on CO2 elimination

Frequency controls the time allowed (distance) for the piston to move.

Therefore, the lower the frequency, the greater the volume displaced, and the higher the frequency, the smaller the volume displaced.

Theory of operation

Oxygenation and CO2 elimination have been demonstrated to be decoupled with HFOV

5 Hz versus 15 Hz: does it matter?

Meyer J et al. PediatrRes 2006; 60: 401–406

Mean airway pressure, amplitude and frequency

MAP (CDP): recruits alveoli/airways and maintains alveolar volume it is closely related to lung volumes and oxygenation

Amplitude: there is a close relationship between pressure amplitude and tidal volume

tidal volume depends on: 1) the volume displaced by the piston or diaphragm,

2) the resistance of the airways,3) the compliance of the ventilator circuit, and4) the patient’s lung mechanics

therefore: search for visible chest vibrations

change amplitude to control ventilation (PaCO2)

Bouchut JC et al. Anesthesiology 2004; 100:1007-12

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How to set initial MAP when switching to HFOV

Recruitment concept during HFO


Andreduce FiO2!

A recruitment procedure in iRDS

Drop in SO2

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e a

bove

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105

Recruit first the lung and then keep open the lung at the lowest pressure necessary!


1) Lower FiO2 before CDP (=MAP)

Some bedside rules:

4) If you’re “lost” - always decrease CDP first!

3) Try to work always the highest frequency possible - increase the amplitude in a first step to correct for high pCO2

2) Always try to define lung closing pressure to assure that you will use lowest pressures required

The clinical experience:

HFO vs CMV

Elective HFOV vs CMV: Death or CLD at 36 w GA or discharge

Favors HFO Favors CMV

All trials

With volume recruitment

Cumulative Meta-Analysis: Incidence of CLD

Bollen et al. AJRCCM 2003; 168: 1150–1155

Henderson-Smart DJ Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD000104. DOI: 10.1002/14651858.CD000104.pub2.

Elective HFOV versus CMV

CLD at 36-37 wks PMA or discharge



CLD at 36-37 wks PMA or discharge

35% 39% NNT 25



Combined Outcome: Death or CLD at 36-37 wks PMA or discharge

HFOV compared with CMV for Diffuse AlveolarDisease or Air Leak in Pediatrics Arnold et al. Crit Care Med 1994;22

Protocol: MAP was set 4-8 cm H2O > CMV-MAPDecrease FiO2 before MAP

Results:No difference in Death, Length of Vent., Air Leak.

Significant improvement in oxygenation with HFO over time.*

Less need for O2 at 30 days with HFO.* * p<0.05

HFOV is safe and improves oxygenation as well as outcome

58 Children (29 CMV, 29 HFO)

MOAT II: Overall Survival

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CV

HFOV

30d p=0.05790d p=0.078

HFOV CVN 75 73 P/F 114 (37) 111 (42)

Derdak S Am J Respir Crit Care Med 2002; 166:801–808

Predictors of Outcome

1) Oxygenation Index Response

(OI = )

2) Entry Indicators of Compliance

(Peak Inspiratory Pressure)

MAP x FiO2 x 100 PaO2

MOAT II: Predictors of Outcome

Derdak S Am J Respir Crit Care Med 2002; 166:801–808

MOAT II: Survival - PIP 38 cmH20 (post-hoc)

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30d p=0.01990d p=0.026

HFOV

HFV-Meeting2001

Fedora M Bratisl Lek Listy 2000; 101: 8-13

Early (< 24 h) versus late (>24 hours) intervention in pediatric ARDS

Metha S et al. Crit Care Med 2001; 29:1360 –1369

Time concepts for lung protection

Neither a ventilation strategy nor a mode can repair the injured lungs

Katzenstein AL et al. Surgical pathology of non-neoplastic lung disease. Saunders, Philadelphia, 1982

First Intention HFO with early lung volume recruitment

Demographic data and severity of lung disease

all patients HFO (n=32) CMV (n=39) p - value

Birth weight (g) 981 ± 242 965 ± 254 n.s.*

Estimated gestational age (weeks) 27.7 ± 2.0 27.7 ± 1.8 n.s.*

Antenatal steroid treatment, no (%) 13 (41) 14 (36) n.s.#

APGAR score < 4 at 1 min, no (%) 13 (44) 17 (44) n.s.#

APGAR score < 6 at 5 min, no (%) 7 (22) 5 (13) n.s.#

Degree of HMD (1 - 4) on CXR 2.9 ± 0.8 3 ± 0.9 n.s.*

aA-ratio (first blood gas analysis) 0.16 ± 0.09 0.20 ± 0.16 n.s.*

Values are given as mean ± SD, or as the number (percentage) of patients; * unpaired t-test; ** Chi-square;

# Fisher's exact

Rimensberger PC et al. Pediatrics 2000; 105:1202-1208

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Mean airway pressure PaO2/FiO2 ratio



Observational study, historical cohort: 71 premature infants with RDS at birth

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n=3

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oxygen dependency

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days of ventilation

• HFO• CMV

• HFO• CMV



Survival and CLD Morbidity

all patients HFO (n=32) CMV (n=39) p - value

survivors to 30 days HFO (n=27) CMV (n=35) Ventilation (days) 5 (3-6) 14 (6-23) 0.0004 * Oxygen dependency (days) 12 (4-17) 51 (20-60) <0.0001 * Oxygen at 28 d, no (%) 6 (22) 22 (63) 0.002 #

survivors to 36 weeks PCA HFO (n=27) CMV (n=34) CLD; Oxygen > 36 weeks PCA, no (%) 0 (0) 12 (35) 0.0006 #

Values are given as the median (95% CI) or the number (percentage) of patients; * Mantel-Cox log-rank; # Fisher's exact



Recruitment bei der Hyalinen Membranenkrankheit (RDS)28 wks GA, 8 hours after birth, on HFOV, no surfactant received

MAP 12 cmH2O, Amplitude 40, FiO2 0.8 MAP 16 cmH2O, Amplitude 28, FiO2 0.21

08’10 08’25

MAP 26 cmH2O

Stepwise increase of MAP Stepwise decrease of MAP

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HFO afterrecruitment

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Rimensberger PC Intensive Care Med 2000; 26; 745-755

CMV afterrecruitment

Recruitment during both, HFO and CMV, follows similar concepts when using small tidal volume ventilation

2. Similar protective effect on histology

1. Similar effect on oxygenation

Rimensberger PC Intensive Care Med 2000; 26; 745-755

Van Kaam A Ped Research 2003

Lung recruitment (open lung concept) during both, CMV and HFO reduces VILI in newborn piglets

PPVCON

PPVOLC HFOOLCLavaged

Van Kaam A Ped Research 2003

Lung recruitment (open lung concept) during both, CMV and HFO reduces VILI in newborn piglets

PPVcon PPVOLC

HVOOLC Controls

pO2

pCO2

OLV improves gas exchange and attenuates secondary lung injury in a piglet model of meconium aspiration

Van Kaam A et al. Crit Care Med 2004; 32:443–449

OLC in a neonatal piglet lavage model

Van Kaam A Biol Neonate 2003;83:273-80

Recruitment and the Open Lung Concept is all about avoiding collapse and overdistention

Recruitment and the Open Lung Concept during HFOV is all about keeping the lung open at the least pressure cost

The difficulty to place the ventilatory cycle within the safe window during CMV when compared to HFOV


Airway pressure (cmH2O)

Vo

lum

e (

l)

(surfactant depleted lung)

ALI

severe(A)RDS


“The beauty of simplicity”

HFOV: Turn 1 knob …

and observe 2 parameters (O2, CO2)

Hickling KG et al. AJRCCM 2001; 163:69-78

Turn then 1 (or 2 knobs) …

and observe 3 parameters (O2, CO2, Cdyn)

Time constant: T = Crs x Rrs

and remember to adapt Ti and Te

CMV: chose your allowable Vt

High frequency oscillatory ventilation (HFOV): How does it work and how to integrate it in the...

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